135266-68-1Relevant articles and documents
A New Protocol for Regio- and Stereocontrolled Aldol Reactions through the Conjugate Addition of Dialkylboranes to α,β-Unsaturated Ketones
Boldrini, Gian Paolo,Bortolotti, Michele,Mancini, Fabrizio,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
, p. 5820 - 5826 (2007/10/02)
A one-pot, two-step procedure, consisting of the 1,4-addition of dialkylboranes to β-substituted (E)-α,β-unsaturated ketones followed by the reaction of the resulting configurationally pure (Z)-(vinyloxy)boranes with aldehydes, is reported.The overall process corresponds to a regio- and stereocontrolled aldol addition of an unsymmetrical ketone to an aldehyde.A concerted 1,4-addition mechanism accounts for the stereochemical outcome of the hydroboration reaction; cyclic enones do not undergo conjugate addition, while (Z)-β-substituted or β,β-disubstituted α,β-unsaturated ketones still react in a 1,4-fashion, but with a slower rate and a lower degree of chemoselectivity with respect to β-substituted (E)-α,β-unsaturated ketones.In the cases of α,β-disubstituted α,β-unsaturated ketones and (E)-(S-phenylthio)cinnamate, which react with dicyclohexylborane to give a mixture of E and Z enolates, an alternative mechanism is proposed.
A New Approach to (Z)-Vinyloxyboranes via 1,4 Hydroboration of (E)-α,β-Unsaturated Ketones. Synthesis of syn Aldols
Boldrini, Gian Paolo,Mancini, Fabrizio,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
, p. 1680 - 1681 (2007/10/02)
(Z)-Vinyloxy boranes are obtained via 1,4-hydroboration of acyclic disubstituted (E)-α,β-unsaturated ketones with dicyclohexylborane or diisopinocampheylborane in tetrahydrofuran, CH2Cl2 or CHCl3 at 20 deg C; treatment of the hydroboration mixture with an aldehyde allows pure syn aldols to be synthesized in good yields, and in excellent enantiomeric excesses, using the latter borane.
